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TORT OF INVESTIGATION NO. 18
1953
STATE OF ILLINOIS
WILLIAM G. STRATTON. Governor
The Silting of Lake Carthage
CARTHAGE, ILLINOIS
J. B. Stall, G. R. Hall, S. W. Melsted and E. L Sauer
A Cooperative Study by
Illinois State Water Survey Division, Soil Conservation Service
United States Department of Agriculture
and Illinois Agricultural Experiment Station
With Local Help From
City of Carthage, Water Department
DEPARTMENT OF REGISTRATION AND EDUCATION
VERA M. BINKS, Director
STATE WATER SURVEY DIVISION
A. M. BUSWELL, Chief
(Printed by the authority of the State of Illinois)
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05030906
Stall, J.B.
THE SILTING OF LAKE
CARTHAGE, CARTHAGE,
ILLINOIS.
DEMCO
CONTENTS
Page
ii
SUMMARY
GENERAL
Introduction
Scope of Investigation
Acknowledgement
1
1
2
RESERVOIR
General Information
2
Reservoir
2
Dam
2
Watershed
2
Methods of Survey
2
Range System
2
Measurement of Sediment
,.
2
Deltas.
2
Sedimentation in the Reservoir
3
Summary of Data
3
Discussion of Lake Sedimentation.
3
Distribution of Sediment
4
History of the Carthage Water Supply
.'..:
6
Period 1890-1925
6
1925—Present
7
Increase in Water Consumption
7
General Considerations
7
Population Trend
7
Water Consumption Per Capita
7
Reservoir Operation and Need
7
General
7
Remaining Useful Life of the Reservoir
8
Streamflow Variability
8
Drought Frequencies
8
Date When Water Shortage May Occur
8
Economic Loss From Sedimentation
9
SEDIMENT CHARACTERISTICS
Analyses Made
9
Origin of Sediment
12
WATERSHED
Introduction
12
Physiography...
12
Soil Groups
12
Slopes
12
Present Land Use
13
Erosion
13
General
13
Gully Erosion
'.
16
Sources of Sediment
17
Conservation
18
RESULTS
Cause of High Rate of Storage Loss
18
Remedial Measures
18
Practicability
18
Raising the Dam.......................................................................................................................18
Other Lakes
18
Dredging
18
Vegetative Plantings
18
Watershed Treatment Program
18
.. Needed Measures....
18
Structures
19
Probable Present Annual Soil Loss
19
Probable Soil Loss Under Proposed Program
19
Reduction of Sediment Reaching Lake
19
Extension of Life of Lake
.".
20
Costs and Benefits of Conservation
20
Present Practices
20
Costs of Conservation
20
Benefits of Conservation
21
Long-Time Economics of Conservation Farming
21
Economics of Conservation
_
21
Recommendations
21
SUMMARY
1. Lake Carthage, the municipal water supply reservoir at
Carthage, Illinois, was built in 1926. The lake has a drainage
area of 2.9 square miles. The original reservoir surface area was
39.7 acres and the capacity was 132.8 million gallons.
Productivity of permanent pastures in the area probably is less
than 50% of that which reasonably could be expected. Reseeding, fertilizing and mowing are needed to gain the potential
yield from these pastures.
2. The 1949 sedimentation survey of this reservoir showed
a capacity loss of 1.03 percent per year. In 23.4 years, the lake
had lost 24.1 percent of original capacity.
13. Indications are that sheet erosion furnishes 82% of the
total sediment reaching the reservoir and that gully erosion
produces 18% of the sediment.
3. The City of Carthage was served from 1898 to 1926 by
an underground water supply. In 1926,. the present Lake Car­
thage and filter plant were constructed and have served the
city's water-supply needs up until the present time.
14. A watershed treatment program in the Lake Carthage
watershed which includes conservation farming methods and
gully-control measures, could probably reduce the total sedi­
ment reaching the lake by 67.7%.
4. The City of Carthage has grown in population from 1,654
in 1890 to 3,214 in 1950. If Carthage continues to grow as other
comparable Illinois cities have in the past the population served
by the water system will reach 9,100 by the year 2000.
15. An important step in establishing a soil conservation
program in this area is soil treatment, that is, the application
of limestone, phosphate and potash in accordance with needs
as shown by soil tests.
5. In the past, the per capita use of water in Carthage has
varied from 21 gallons to 71 gallons per person per day. Con­
sidering per capita use to reach a maximum of 100 gallons per
person per day in the future, municipal pumpage may reach
540,000 gallons per day by the year 1970.
16. Studies of costs and benefits of contour farming in this
area show that contour farming alone, contour strip cropping
and terracing result in higher crop yields and do not increase
the over-all cost of farm operation. Corn, soybeans, oats and
wheat yields were increased 12%, 13%, 16%, and 17% respec­
tively from contouring. Labor, power and machinery costs per
crop acre averaged $1.58 lower at 1945 prices on the farms that
were farming on the contour.
6. As of 1952, Lake Carthage has sufficient capacity to satisfy
the entire demands on the lake during a drought which can be
expected once in four years. From this standpoint, the Lake
Carthage situation seems very serious, and action will be nec­
essary soon to prevent a water shortage.
7. The storage capacity displaced each year by sediment in
Lake Carthage would cost about $950 to replace at the present
time.
8. Chemical analyses of samples of the reservoir sediment
show them to be quite acid and low in organic carbon and
nitrogen, indicating that they are not predominately surface
soil materials.
9. Poorly drained prairie soil-groups occupy a large portion
of the watershed. The Herrick silt loam soil group occupies
63.5% of the area.
10. A conservation survey of the watershed shows that
nearly 80% of the watershed area has less than 4% slope.
11. The survey shows that 86.6% of the watershed is con­
sidered safe for continuous cultivation if conservation measures
are instituted. At the time of the survey, 98.1% of the land
was being cultivated.
12. The conservation data indicate that a disproportionate
amount of moderate and severe erosion was found in pastures.
17. One study of a farm on land similar to that in the Lake
Carthage watershed showed that during a ten-year period the
crops grown yielded only 94% of the county average before a
conservation program was started and 114% afterwards—a
gain of 20%.
18. It is recommended that the City of Carthage engage a
qualified professional engineer to investigate the adequacy of
the present water supply system to furnish the present and
future needs of the city and to report on the most economical
method for maintaining an adequate water supply.
19. It is recommended that the City of Carthage undertake
immediately the application of a watershed treatment program
on the drainage area of Lake Carthage to reduce sedimentation
and prolong the ultimate life of this lake and the length of time
it can be used for the public water supply. It is suggested that
this program be carried out by (1) financial assistance from the
City to the local soil conservation district for intensified con­
servation efforts on this watershed, or (2) purchase of the
watershed or much of the critical erosion area by the City for
application of the needed conservation measures.
1
THE SILTING OF LAKE CARTHAGE
CARTHAGE, ILLINOIS
by
J. B. Stall, Assistant Engineer, Illinois State Water Survey Division, Urbana, Illinois.
G. R. Hall, Sedimentation Specialist, Soil Conservation Service, Milwaukee, Wisconsin.
S. W. Melsted, Associate Professor of Soil Analysis Research, Agronomy Department, College
of Agriculture and Agricultural Experiment Station, University of Illinois,
Urbana, Illinois
E. L. Sauer, Project Supervisor, Research, Economics of Soil Conservation, Soil Conservation
Service and Illinois Agricultural Experiment Station Cooperating, Urbana,
Illinois.
GENERAL
INTRODUCTION
Need for Data. Nature's perpetual cycle of producing natural
resources continues year after year furnishing man with an end­
less source of existence. We can not blame nature therefore for
the scarcities which present themselves because of man's waste­
fulness. Two of our most basic resources, soil and water, are in
many instances being depleted because of such wastefulness.
The investigation discussed in this report is concerned with
problems arising from loss of soil from a watershed, the conse­
quent reduction in the productive capacity of the soil, and the
resulting sediment deposition in a municipal reservoir, which
reduces its capacity for storing the water needed by the City
of Carthage, Illinois.
It would seem obvious that due to the increased demand
for products of the soil, corrective measures should be taken to
prevent the movement of this fertile topsoil from its place. In­
tensive agricultural use of the land in the past without ade­
quate soil conservation measures has placed our resources in a
very precarious position. Conservation of resources can not be
concerned with present day needs alone, but must be consider­
ate of future demands.
Most of the impounding reservoirs in Illinois have been con­
structed in the past two or three decades. Engineers chose
logical locations for such reservoirs by considering the availa­
bility of water, distance from city, subsoil conditions for dam
foundation, peak rates of runoff from watershed, population
trends and cost of storage furnished.
Within the past few years it has become apparent that
deposition of sediment in reservoirs can cause disastrous results.
The sediment is rapidly replacing the space set aside to store
water. As population and water consumption increase the need
for a larger reserve of water storage will be required. This factor
is usually taken into account in the design of a reservoir, but
the rapid loss of storage space due to sedimentation if omitted
from design will more than offset any such allowances. This
would mean that in the event there was an increase in popula­
tion or consumption the water supply would be inadequate.
Many towns are today suffering from water shortages for this
very reason even though their reservoirs were designed to han­
dle water needs for years to come.
The seriousness of erosion in Illinois and the consequent
rapid reservoir sedimentation led the Illinois Water Survey
Division, the Illinois Agricultural Experime'nt Station and the
Soil Conservation Service to join in 1936 in a cooperative study
to determine the effects of different watershed and climatic
factors on the rate of sediment production and the rate of sedi­
mentation of reservoirs. The sedimentation survey of Lake
Carthage was made under this program.
SCOPE OF INVESTIGATIONS
Lake Survey. A preliminary survey was carried out on
Carthage Reservoir in May 1949 to determine the need for a
detailed survey and it was evident that the lake was suffering
from a loss of capacity due to sedimentation. A detailed sedi­
mentation survey was conducted at the Carthage Reservoir in
July 1949. Surveys were made at the request of officials of the
City of Carthage to determine the adequacy of the lake for
water supply for the City.
The detailed survey was made by a field party of the State
Water Survey Division and the City of. Carthage. Water depth
and sediment thickness were measured along thirteen ranges
on the lake. Cross-sections were used to determine the original
capacity of the reservoir, the present capacity of the reservoir
and consequently the volume of sediment in the lake. The sur­
face area of the lake was determined from aerial photographs
of the lake. In carrying out the survey a permanent marking
system was installed so that in the future years resurveys may
be made to measure the sediment accumulation at that time.
By analyzing the past trend in water consumption for the
City of Carthage it was possible to determine the probable
future water demand for the City. A study of this future water
demand in conjunction with the present rate of reservoir stor­
age depletion was made to show the approximate dates at which
the lake will no longer be sufficent to supply the water needs
of the city in case of droughts of various severities.
Watershed Survey. To determine the watershed sources from
which the sediment originates, the Soil Conservation Service
conducted a conservation survey of the watershed in 1949.
These data on soils, slopes, land use, erosion and conservation
practices give a very complete picture of the agricultural use
of the farmlands on the watershed. An analysis of these data
has been made to show specific problem areas where the soil
losses from erosion are great and conservation measures would
be particularly effective. By means of these data, it is possible
to point out definite soil and water conservation measures that
would effectively reduce the soil losses.
An additional study has been made by the Soil Conservation
Service of the land use history of the watershed during the past
twenty-four years while Carthage Reservoir has been in exist­
ence. This analysis shows the trend in land use of the watershed
for this period. Its interpretation in light of the measured rate
of sedimentation aids in developing recommendations for land
use changes which would be most effective in reducing soil
losses.
Sediment Samples. During the course of the survey a series
of eleven sediment samples were taken from various parts of
the lake by means of a special sampler. Chemical and physical
analyses of these samples have been made by the Illinois Agri­
cultural Experiment Station. An analysis of the texture, col­
loidal content, volume-weight and plant food constituents of
the sediment gives significant indication of the watershed
sources of the sediment deposited in the reservoir.
Interpretation of Results. The final interpretation of the
silting problem at Carthage Reservoir has been made on the
basis of the complete reservoir and watershed survey data by
the three cooperating agencies. Results are presented so as to
be most helpful to reservoir owners. Several remedial measures
such as raising the spillway, dredging, and application of a
complete watershed protective program are discussed.
2
ACKNOWLEDGEMENT
City of Carthage. The agencies conducting this survey wish
to acknowledge the generous cooperation of the municipal au­
thorities of Carthage, particularly the City water department
in authorizing and expediting this survey. Mr. Roy Metz,
Waterworks Superintendent, was most helpful at all times in
aiding the conduct of the survey.
State Water Survey Division. The survey of this reservoir
was carried out by a field crew of the State Water Survey
Division consisting of J. B. Stall, Chief of the party, T. E.
Young and J. R. Singer, Engineering Assistants. The computa­
tion of the volume of water and sediment in the lake was
carried out in the office. The compilation of the engineering
sections of this report plus the preparation of the report for
publication has been done by Mr. Stall under the supervision
of H. E. Hudson, Jr., Head, Engineering Sub-Division.
Soil Conservation Service. Various officials of the U. S. De­
partment of Agriculture, Soil Conservation Service have con­
tributed to this study in many ways. The Sedimentation Section
of the Office of Research in Washington furnished the special­
ized field equipment and aerial photographs for the survey
work. Mr. L. C. Gottschalk, Head of the Sedimentation Sec­
tion, gave technical assistance to the field party during the con­
duct of the survey and to the authors in the preparation of
this report.
Mr. B. B. Clark, State Conservationist, cooperated by au­
thorizing the conservation survey of this watershed by Soil
Conservation Service personnel and was helpful in many ways
to the authors in the preparation of the report. The field work
of the watershed survey was carried out by Mr. A. A. Agathen,
Soil Surveyor, during 1949. Mr. A. A. Klingbiel, State Soil
Scientist, aided in the analysis of the watershed survey data.
Mr. G. R. Hall, Sedimentation Specialist, Milwaukee Re­
gional Office, prepared the watershed section of this report in­
cluding the conservation program recommendation for the
watershed.
Dr. E. L. Sauer, Research Project Supervisor, Soil Conserva­
tion Service and Illinois Agricultural Experiment Station co­
operating, carried out the study of land use and conservation
history of the watershed. This study entailed both field visits
and study of public records and their interpretation. Dr. Sauer
also prepared the data in this report concerning the costs and
benefits of conservation.
Illinois Agricultural Experiment Station. Samples of sedi­
ment in the lake were procured by the field party. These sam­
ples were analyzed in the laboratory of the Illinois Agricultural
Experiment Station. The interpretation of these analyses and
the preparation of the section of this report dealing with the
sediment samples were carried out by Dr. S. W. Melsted, As­
sociate Professor of Soil Analysis.
Hancock County Soil Conservation District. The directors
of the Hancock County Soil Conservation District have aided
this study by authorizing the use of personnel assigned to the
District for carrying out the conservation survey of this water­
shed.
RESERVOIR
GENERAL INFORMATION
Reservoir. The reservoir is located about one mile northwest
of the City of Carthage in the west half of Section 13, T. 5 N.,
R. 7 W. The dam is located in the northeast corner of the north­
west quarter of Section 13. The reservoir extends approximately
4,000 feet generally south from the dam with one major sidearm extending west from the dam about 2,000 feet. The lake
has a width of approximately 500 feet at the dam and the
major arm has a width of about 250 feet. The general location
of the reservoir with respect to the city of Carthage is shown
in Figure 1. The lake is located on a tributary to Long Creek
which flows east from the lake into the LaMoine River and
thence southeastward into the Illinois River.
Dam. The dam extends in a generally northwest-southeast
direction and has a total length of about 500 feet. The upstream
face of the dam is faced with concrete to prevent wave erosion.
A concrete spillway having a total length of about 65 feet is
located at the southeast end of the dam. The waterworks in­
take is located near the dam.
Watershed. The reservoir has a total watershed area of 2.90
square miles. The watershed extends generally west and south
from the lake.
METHODS OF SURVEY
Range System. In determining the original (1926) and the
present water and sediment volumes the range method of sur­
vey was utilized. This method of survey was developed by the
Soil Conservation Service and is described in detail in their
Bulletin No. 524 "Silting of Reservoirs."1 The record of sedi­
mentation in this lake is based on a system of 13 sediment
ranges which were established by the field party for the pur­
poses of this survey. The location of the range system on the
lake is shown in Figure 2.
1
Eakin, H. M., Silting of Reservoirs, U. S. Department of Agriculture Tech­
nical Bulletin 524, Revised by C. B. Brown, 168 pp. illustrated. Washington,
U. S. Government Printing Office, 1939. Appendix.
The base map for this survey consisted of an enlarged aerial
photograph having a scale of one inch equals 200 feet. All sur­
vey stations were located on the map by means of visual ob­
servation of various topographic features. These locations were
checked in the course of the survey by means of planetable and
telescopic alidade. All triangulation stations and range ends
were marked permanently in the field with concrete posts 4½
inches square and 4½ feet long. These posts were set into the
ground with about one foot exposed. Station identification
numbers were stamped permanently into the brass caps con­
tained in these posts. This permanent marking system will be
of value in the future when it becomes desirable to relocate the
present sediment ranges to make a resurvey of Lake Carthage
along these same ranges.
Measurement of Sediment. Along each sediment range at
intervals of 25 feet the water depth and sediment thickness were
measured with a sounding pole. This consists of a l½-inch
diameter calibrated aluminum pole constructed in sections to
give a total length of 30 feet. This pole is shown in use in Figure
3. The pole is lowered into the water until it strikes the top of
the sediment deposit and thus the present water depth is meas­
ured. The pole is then thrust on through the soft sediment until
it strikes the hard soil of the original reservoir bottom. In this
manner the present water depth and the sediment thickness are
measured. As the boat is rowed across the range a cross-section
of water depth and sediment thickness is obtained. A total of
186 sediment measurements were made on the 13 ranges on
Lake Carthage.
Deltas. The surface area of the reservoir had been reduced
very noticeably at the heads of the two main arms of the lake.
The loss of surface area in the reservoir as a result of this delta
formation was determined by remapping the present water line
at the upper end of these arms. The volume of these deposits
was calculated by use of the range formula which was used on
all segments of the lake. The deposits in these areas which oc­
curred above spillway crest elevations were not considered
large enough to be mapped and calculated separately.
3
FIG. 1. LAKE CARTHAGE LOCATION.
SEDIMENTATION IN THE RESERVOIR
Summary of Data. Table 1 is a summary of the sedimenta­
tion data obtained from this survey of Lake Carthage together
with data derived therefrom which are pertinent to the sedi­
mentation problem in this lake. Several of the significant find­
ings shown in this summary are:
1. At the present spillway crest elevation the surface area
of the reservoir has been reduced from 39.7 acres to 36.1
acres in the 23.4 years which the lake has been in exist­
ence.
2. The capacity of the reservoir for water storage has been
reduced from 132.8 million gallons to 100.8 million gal­
lons, or 24.14 per cent.
3. The sediment accumulation in the lake represents an
average annual rate of sediment production of 93.3 cubic
feet per acre from the watershed area.
Discussion of Lake Sedimentation. The total volume of sedi­
ment deposited in a reservoir is in general dependent upon three
factors:
1. The total amount of soil which is removed from the lands
of the watershed by erosion.
2. The effectiveness of the stream system within the drain­
age area in transporting the soil particles from the land
to the reservoir.
3. The effectiveness of the reservoir itself in trapping and
.retaining the sediment which flows into it.
The first of these items has been studied in detail for the Lake
Carthage watershed and is discussed in a later section of this
report. The effectiveness of the drainage system in transporting
sediment to the reservoir depends on the hydro-physical char­
acteristics of the watershed. Channel density is often used as
a measure to express this. Authoritative authors in the field of
reservoir sedimentation have selected the ratio of reservoir
capacity to the total drainage area as a significant ratio for use
in comparing different reservoirs regarding the third item men­
tioned above.2 The capacity-watershed ratio, or C/W ratio, is
usually expressed in units of acre-feet of storage per square
mile of drainage area. Other factors being equal, the C/W ratio
reflects the detention time or the total period of time that the
waters from the watershed are stored in the lake. If the waters
of the inflowing stream are detained in the lake for a long period
of time all of the suspended sediment particles including clay
and colloids have time to settle out and deposit on the bottom
of the lake whereas, if the waters are retained in the lake for
only a few days only the coarser particles such as sand, silt
and coarser clays have time to settle out.
2
Brown, Carl B., The Control of Reservoir Silting, U. S. Department of Agri­
culture. Misc. Pub. No. 521, Washington, D. C, 1944.
4
FIG. 2. LAKE CARTHAGE—1949 SEDIMENTATION SURVEY.
It is noted from Table 1 that Lake Carthage was designed
and constructed with an original capacity-watershed ratio of
138 acre-feet per square mile.
In Table 2 the sedimentation results of Lake Carthage are
shown in comparison to several other Illinois reservoirs that
have recently been surveyed.
From the above discussion it is noted that with a given unit
rate of sediment production a low capacity reservoir on a large
watershed area will lose capacity much faster than a high capac­
ity reservoir on a small watershed. It will be noted from Table
2 that reservoirs at Eldorado, Carbondale, and West Frankfort,
all have capacity-watershed ratios of about 400 acre-feet per
square mile. These reservoirs have annual capacity loses of 0.48
per cent, 0.63 per cent, and 0.33 per cent. On the other hand,
Lake Carthage with an original capacity-watershed ratio of
138 has suffered an annual loss of capacity of 1.03 per cent.
Conversely Spring Lake at Macomb with a much smaller orig­
inal capacity-watershed ratio of 30-acre-feet per square mile
has suffered a much larger rate of storage loss, 2.3 per cent per
year. Figure 4 shows graphically the comparison of the annual
rate of storage loss at Lake Carthage to the other reservoirs
shown in Table 2.
Distribution of Sediment. Cross sections indicate a rather
even distribution of sediment throughout the lake. The greatest
loss of storage capacity in Lake Carthage has occurred at the
heads of the two major arms of the lake in Segments 9, 10, and
13, 14 as shown in Figure 2. Segment No. 10 which contains a
large delta area has lost a total of 75 per cent of its original
capacity. Segment 9 has suffered a loss of 69 per cent of its
original capacity. Segment 14 at the upper end of the smaller
arm of the lake has lost a capacity totaling 58 per cent. Segment
1 nearest the dam had the lowest rate of capacity loss, losing
only 13.0 per cent of its original capacity.
In Figure 5 is shown the cross-section of water depth and
sediment thickness along range R 1 - R 2. This range extends
across the main body of the lake immediately above the dam.
(See Figure 2.) It is seen from the cross-section of range R 1 - R 2
that the original water depth of approximately 20 feet along
the major portion of the range has been reduced by a deposition
of sediment approximately 3 feet in thickness along the major
portion of this range.
Figure 6 shows the cross-section of range R 9 - R 10 which
extends across the main body of the lake in the central portion
of the lake. It is seen from this cross-section that the original
FIG. 3. USE OF THE SOUNDING POLE IN
MEASURING SEDIMENT.
5
TABLE 1
Summary of Sedimentation Data
Carthage Reservoir, Carthage, Illinois
Quantity
AGEI
1926-1949
WATERSHED
Total Area2
23.4
2.90
1969
RESERVOIR
Area at spillway level
1926
1949
Storage Capacity at spillway level
1926
1949
Storage Capacity per sq. mile
1926
1949
SEDIMENTATION
Total Sediment
Average annual accumulation
From entire drainage area
Per sq. mile of drainage area 3
Per acre of drainage area3
By volume
By
weight 4
DEPLETION OF STORAGE
Loss of original capacity
Per year
Total
1
2
3
39.7
36.1
Units
Years
Square Miles
Acres
Acres
Acres
406.3
(132.8
308.2
(100.8
Acre-Feet
Mil. Gal.)
Acre-Feet
Mil. Gal.)
138
106
Acre-Feet
Acre-Feet
98.1
(32.0
Acre-Feet
Mil. Gal.)
4.19
1.42
Acre-Feet
Acre-Feet
93.3
2.50
Cubic Feet
Tons
1.03
24.14
Per Cent
Per Cent
FIG. 4. LAKE CARTHAGE STORAGE LOSS COMPARED
TO OTHER ILLINOIS RESERVOIRS.
water depth was approximately 13 feet along the valley flat
and that the original stream channel had a total depth of about
18 feet. Sediment has been deposited along this range to a depth
of about 3 feet for the entire range, the deposit being slightly
deeper in the old stream channel.
In Figure 7 is shown the cross-section of Range R 16 - R 17
which extends across the lake at the extreme upper end as shown
in Figure 2. In this part of the lake the total original depth of
the water was approximately 6 or 7 feet. This has been reduced,
however, to a depth of only about 2 feet at the present time.
It is in this portion of the lake that a major percentage loss has
taken place.
Storage began Spring, 1926.
Average specific weight of sediment
Date of Survey, August 17-23, 1949. equals 49.4 lbs. per cu. ft. based on
Including area of lake.
10 samples obtained in 1949.
Excluding area of lake.
TABLE 2
Lake Carthage Sedimentation Compared to Other Illinois Reservoirs
Watershed area
Sq. Mi.
Original Capacity
Acre-feet
Mil. Gal.
Original C/W ratio
Acre-Feet per Sq. Mi.
Age, when surveyed
Years
Total loss of capacity, Per cent
Annual loss of capacity
Acre-feet
Mil. Gal.
Per cent
Annual sediment production
Cubic feet per acre
Tons per acre
Eldorado
Reservoir
Lake
Carthage
2.23
2.90
Carbondale
Reservoir
3.10
W. Frankfort
Reservoir
4.03
Spring Lake
Macomb
20.2
844
258
406
133
1386
453
1608
526
607
198
453
138
462
399
30
29.0
14.0
4.1
1.3
0.48
149
5.0
23.4
24.1
4.2
1.4
1.03
93
2.5
22.1
13.9
8.8
2.9
0.63
208
7.7
22.9
7.5
6.0
1.9
0.33
109
4.0
20.4
47.3
14.2
4.6
2.3
48
1.4
6
FIG. 5. CROSS SECTION OF RANGE R1-R2.
HISTORY OF THE CARTHAGE WATER SUPPLY
Period 1890-1925. Efforts to develop a public water supply
for the City of Carthage were begun about the year 1890. At
this time a well was drilled to a depth of about 1700 feet. This
well-did not provide satisfactory water however and.it was
abandoned. In 1898 another well was drilled, this to a depth of
1000 feet. This well was located about one block from the
Courthouse square. Although the water from this well was
highly mineralized it furnished the entire public supply for
several years. Mineral analysis of the water taken from this
well in. 1912 showed a total hardness of 741 parts per million,
a total mineral content of 2677 parts per million.
In 1912 a new well was drilled at a location 25 feet north of
the 1000-foot well. This new well was drilled to a depth of 847
feet. The mineral analysis of a water sample obtained from this
new well May 1923 showed it to have a total hardness of 632
parts per million and a total mineral content of 2682 parts per
million.. After the completion of this new well, it was used as a
major source of supply for the city. Water from the new well
reportedly had a more agreeable taste and tarnished fixtures
less than did the water from the old wells.
The two wells owned by the City served to furnish the
entire public supply for several years. However, in 1919 Mayor
W. H. Hartzell and the members of the city council began to
investigate the possible improvement of the City's supply. In
July 1919, the city council passed a resolution employing the
firm of Fuller and Beard, Consulting Engineers of St. Louis,
Missouri to make a rather complete study of the water works
situation. The City requested the engineers "to prepare a re­
port with your recommendation as to the best source of water
supply for the City of Charthage and suggest the design and
capacity of the pumping plant and equipment; to prepare a
plan of the City of Carthage showing the proposed extension of
water mains with the location of the valves and fire hydrants
and such other incidentals as are necessary to make a complete
waterworks improvement."
In making their study the Fuller and Beard engineers in­
vestigated the possibility of a water supply from wells and
FIG. 6. CROSS SECTION OF RANGE R9-R10.
FIG. 7. CROSS SECTION OF RANGE R16-R17.
7
from several suface water sources. Their report stated: "As for
the possibility of securing an adequate supply of a good potable
water from wells within the vicinity of Carthage, you, as well
as your neighboring cities of Macomb and Mt. Sterling, have
well demonstrated it is not practical; that the water obtained
from wells 200 feet deep while of a fair quality it cannot be ob­
tained in sufficient quantity to supply your needs and the water
from deeper wells is so mineralized as to make it unfit for domes­
tic use."
As one possibility, the Fuller and Beard engineers suggested
the construction of a channel dam on the main stem of the
Lamoine River approximately 5½ miles east of Carthage. Their
second proposal suggested the construction of an impounding
reservoir on Long Creek about one mile north of the present
city of Carthage. The location of this dam would be approxi­
mately one-fourth mile west of the present State Highway No.
94, on the Long Creek. This report recommended the construc­
tion of the reservoir on Long Creek. This reservoir would have
a capacity of 40 million gallons and have a drainage area of
about 12 square miles.
The report gave the following cost estimates: The total cost
of dam and filter plant and pipe line construction on the La­
moine River site, $122,934. The total cost of the dam, lake,
filter plant and pipe line construction on the Long Creek site,
$74,240, and in either case an estimated cost of extensions to
the city distribution system, including an elevated tank, $49,288.
Upon receipt of this report by the City officials, no definite
action was taken, the primary consideration probably being that
the costs were considered prohibitive.
1925-Present. In 1925 the City contracted for the construc­
tion of the present Lake Carthage and water filtration plant.
The lake and treatment plant were designed by the Caldwell
Engineering Company of Jacksonville, Illinois. The treatment
plant is located near the west end of the dam and treatment
consists of coagulation, filtration', and chlorination. The plant
is connected to the city by means of an 8-inch diameter pipe­
line. An elevated steel tank of 80,000 gallons capacity was con­
structed at this time on city property at the site of the old
waterworks within the city.
In 1949 several improvements and additions were made to
the water treatment plant. This work was carried out with the
advice of the Pappmeier Engineering Company of Galesburg,
Illinois. At present the treatment plant has a rated capacity
of 720,000 gallons per day. An analysis of a water sample col­
lected from Lake Carthage in 1948 showed a total hardness of
100 parts per million.
The ownership of the waterworks of Carthage has been with
the municipality since its very beginning.
in the past. The past population curves for the cities of Macomb,
Canton, Sterling and Monmouth are shown in Figure 8. By
this means it is seen that the population of Carthage may
reach 6,500 by the 1980, 9,100 by the year 2000, and 14,000 in
the year 2030.
Water Consumption per Capita. The total municipal pumpage in any year divided by the population gives the rate of per
capita water consumption. Factors affecting per capita con­
sumption are the same as those affecting the total water demand.
In the past, repeated studies have been made correlating the
per capita consumption and the total population. A recent
study in Illinois has shown that the per capita consumption of
water is not necessarily a function of the total population of
the community.3 The per capita consumption is most closely
correlated with the net effective family buying income of the
area. If the economic development of the area increases this
average purchasing power, then the per capita water consump­
tion can be expected to increase, otherwise not. Table 3 shows
the variation in consumption per capita at Carthage in past
years. This has varied from a low of 21 gallons per person per
day in 1920 to a high of 71 gallons per person per day in 1950.
While per capita consumption has shown a steady increase
over the period shown in Table 3 it is not believed that such a
trend can continue indefinitely. For estimating future water
demand a constant value of 100 gallons per person per day
was used.
The values of future populations from the graph in Figure 8
multipled by the average daily consumption of 100 gallons
gives the average annual pumpage to be expected in future
years. Calculated in this manner the total municipal pumpage
may reach 540,000 gallons per day by 1970, and 760,000 gal­
lons per day by 1990. The assumption that the total per capita
consumption will not increase above 100 gallons per day is
considered conservative. There remains the possibility however
that this figure may be exceeded. This would increase the
future water requirements of the city.
TABLE 3
Water Consumption at Carthage
INCREASE IN WATER CONSUMPTION
General Considerations. The future demand for water in the
Carthage area is dependent upon many factors such as the
presence and possible expansion of water-using industries, the
location of new industries in the area, the increase in popula­
tion, the water rates, the water quality, and the adequacy of
the water supply. A city of limited water supply is a city of
limited growth and likewise the early development of the water
resources of an area stimulates the economic growth of the
area.
Population Trend. The U. S. Bureau of Census figures show
that the population of Carthage has increased from 1654 in
1890 to 3214 in the year 1950. This increase has been plotted
in Figure 8. The future growth of the City of Carthage to the
year 2030 as shown in Figure 8 is based on consideration of the
past growth of other cities in the area. It is believed that the
most reliable method for determining future growth of the City
of Carthage is to compare it to the growth of other comparable
cities in this part of Illinois which have experienced such growth
Year
Population
Total Pumpage
G
1000 Gal.
Per Day
1920
1925
1930
1935
1940
1945
1950
2129
2175
2240
2410
2575
2895
3214
45
55
62.4
81.2
109.3
129.3
221.9
Gallons
per Day
Per Capita
21
25
28
34
42
51
71
RESERVOIR OPERATION AND NEED
General. The function of any water-supply impounding
reservoir is to store runoff from the watershed during wet
periods when the stream flow exceeds the consumption. The
water thus stored is available for use during dry periods when
the flow of water in the stream is insufficient to furnish the
user's need. Consequently, to obtain the full value from a
reservoir, it should be designed so that the runoff coming into
the reservoir is large enough to overbalance the consumption
plus the losses from evaporation and seepage. The storage vol­
ume of the reservoir should be large enough to fulfill all needs
during the driest season for which it is designed.
3
Larson, B. O. and Hudson, H. E., Jr. Residential Water Use and Family
Income. Journal American Water Works Association, August, 1951, Vol.
43, No. 8.
8
FIG. 8. CARTHAGE POPULATION T R E N D .
The best indication of the usefulness and the need of a watersupply reservoir is the fluctuation of the water level in the lake.
Ever time the water level is drawn down in the reservoir, de­
mand is exceeding the inflow. This means there would be a
water shortage if the lake were not present. Likewise the best
indication of the impending inadequacy of a reservoir is the
occurrence of serious drawdowns during dry periods when in­
flow is small and consumption is large. Sediment deposits steal
needed storage space. This loss of water storage capacity causes
progressively heavier drawdowns during dry periods.
Under limiting conditions of precipitation, runoff, evapora­
tion, seepage, availability of land, and prevailing rate of sedi- .
ment production, the problem of developing a dependable water
supply is not a simple one. If the reservoir capacity is too large
in relation to the size of drainage area, it may never fill to ca­
pacity, thus representing an economic loss to the owners. If
the reservoir capacity is too small, loss of capacity due to sedi­
mentation will probably be high and the reservoir will rapidly
become useless.
Remaining Useful Life of the Reservoir. The storage ca­
pacity of Lake Carthage is now being reduced by 1.03 per cent
per year as shown in Table 1. Figure 9 shows graphically this
reduction in lake capacity assuming that the rate of deposition
will continue at the present rate. It is seen from Figure 9 that
at the present rate of sedimentation, the capacity of the lake
would be reduced to 87.5 million gallons in the year 1960, 77.1
million gallons by the year 1980, and 66.7 million gallons by
the year 2000. As the storage capacity in the lake decreases
and the total water consumption for the city increases, it is
seen that at some time in the future a water shortage could
occur. The lake owners who are faced with the problem of pro­
viding an adequate source of water supply must know the future
date at which such a water shortage may occur in order that steps
may be taken to prevent the water shortage. The total length
of time for which the reservoir can furnish the total supply of
water needed by the city is termed the "useful life of the reser­
voir." This term is used because at the end of this time the
lake will no longer be able to furnish the total needs of the city.
A future water shortage will occur only during a dry period
of such severity that the minimum inflow to the reservoir is
insufficient to furnish the entire pumpage for the city plus the
losses from evaporation and seepage. As such a shortage nears,
the water level in the lake is drawn down. Past records at Lake
Carthage show that only in the past few years has the water
level been drawn down seriously. The "critical usage period"
or the length of time in months during which the water level
may be drawn down and eventually the lake emptied, is de­
pendent upon, first of all, the total water demands as explained
above. The second major factor affecting the occurrence of the
water shortage is the precipitation expected on the watershed
and the flow characteristics of the streams which feed the lake.
Stream Flow Variability. At the present time there are in
existence approximately 170 gaging stations on Illinois streams.
After records at a particular station have accumulated for a
number of years, an analysis is made of the flow characteristics
of the stream at that point. Such flow records are extremely
valuable in designing a reservoir, in determining the total flow
which can be expected into a reservoir at a particular point on
the stream. This stream-gaging work is carried out by the
United States Geological Survey in cooperation with state and
local agencies. The primary sponsor for stream-gaging stations
in Illinois is the State Water Survey.
In a recent publication of the State of Illinois, a detailed
analysis was made of the flow characteristics of twenty-eight
Illinois streams.4
Very few gaging station records are available in Illinois on
watersheds as small in size as the 2.9 square-mile watershed of
Lake Carthage. However the method devised by Mitchell in
the above publication was used to determine the probable flow
characteristics of the Lake Carthage basin. As an index station
in this stream flow analysis the 27-year record was utilized
from the Lamoine River at Ripley covering the years 1921
through 1947. Although the total watershed of the Lamoine
River station at Ripley is 1,310 square miles, this record was
used to determine the flow characteristics of a much smaller
watershed, namely the Gimlet Creek near Sparland, Illinois
which has a watershed of 5.3 square miles. The Gimlet Creek
station at Sparland was chosen because it was the smallest size
basin on which records were available which would lend them­
selves to this type of analysis. The synthetic flow records from
Gimlet Creek were used to determine the probable lo v flows
on the Lake Carthage drainage area.
Drought Frequencies. In analyzing the severity of droughts
it is common to refer to the various droughts as having an oc­
currence frequency; that is, a certain drought can be said to
have a recurrence frequency of 10 years when such a drought
occurs once during every 10-year period. Droughts of lesser
severity can be expected at smaller intervals of 5, 3, or 2 years.
The more severe droughts which furnish much less runoff may
occur only once in 25, 50 or even once in 100 years.
Date When Water Shortage May Occur. The performance of
Lake Carthage in furnishing the increasing municipal pumpage
plus evaporation losses during low flow periods having various
occurrence frequencies has been analyzed as a part of this
study. The results of this analysis are shown in Figure 10.
Reference to Figure 10 reveals that in the present year 1952,
Lake Carthage is adequate to furnish the entire demands on
the lake during a drought of such severity that it might occur
once in every 4 years. By the year 1960, city pumpage demands
4
Mitchell, William D., Water Supply Characteristics of Illinois Streams,
State of Illinois, Department of Public Works & Buildings, Springfield,
•Illinois, 1950.
9
FIG. 10. RECURRENCE FREQUENCY OF DROUGHTS WHICH
MIGHT CAUSE A WATER SHORTAGE AT CARTHAGE.
FIG. 9. DECREASE IN STORAGE CAPACITY DUE TO
SEDIMENTATION—LAKE CARTHAGE.
will probably have increased to a point where the total demand
can no longer be furnished during a drought having a recur­
rence interval of 4 years. In 1960 the lake would be adequate
to furnish the supply during a drought having a frequency of
2.8 years. By the year 1970 city pumpage will have increased
and the lake capacity will have decreased to the point where
the reservoir can furnish the water demand of the city only
during a drought having a frequency of once every 2 years.
The situation depicted by Figure 10 is considered very serious
in view of the fact that in the present year a water shortage
may be expected to occur during a drought which can be ex­
pected any year within the next four years. In modern water
supply planning, it is normally considered necessary to provide
adequate storage to suit the needs of a municipality during a
drought expected only once in 25 years or once in 50 years. It
is not believed desirable for a municipality to remain dependent
upon a source of supply which may be inadequate once in every
four years or less. From this standpoint, the Lake Carthage
situation seems very serious and action will be necessary soon
to prevent a water shortage.
ECONOMIC LOSS FROM SEDIMENTATION
At the time of the construction of the lake, in 1926, a bond
issue of $77,000 was floated to cover the cost of the lake, the
treatment plant and the eight-inch main connecting the treat­
ment plant to the city distribution system. No breakdown is
available stating the individual costs of the three items and so
the actual cost of the lake itself is not readily available. For
analysis purposes it is assumed that the total lake costs includ­
ing land acquisition, clearing and dam and spillway construc­
tion amounted to $35,000.
The original lake capacity, as determined by the survey was
132.8 million gallons. If the lake cost $35,000 the original stor­
age cost $263 per million gallons. This means that the sediment
which has deposited in the lake each year Has destroyed storage
space which cost $361. This amount of damage is occurring
every year.
Replacement of this lost storage capacity as well as the
building of additional facilities at present prices would be ex­
pensive. In 1926 when Lake Carthage was constructed the
general cost of such work was much less than at present. One
of the most widely used indices of such construction cost in the
Engineering News-Record Construction Cost Index which is
computed monthly and considers current prices of certain basic
construction commodities such as cement, steel, labor, etc.
In 1926 the Construction Cost Index was 210 (based on the
year 1913 = 100)5 and in March 1952 this index had risen to
551. In consideration of this increase in cost the Lake Carthage
storage capacity destroyed each year would cost $947 to re­
place at the present time. Applying the same increase in cost
figures to the original cost of the reservoir, the cost today to
build a new reservoir of the same capacity would be $92,000.
SEDIMENT CHARACTERISTICS
Analyses Made. Sediment samples were taken from severa
locations within the reservoir, as shown in Figure 2. These
samples were analyzed chemically for total carbon, total nitro­
gen, base-exchange capacity, total exchangeable- bases, pH,
available potassium, and available phosphorus. The volumeweight and the percent of sand, silt, and clay were also de­
termined. The data are given in Table 4.
There is considerable variation in the chemical properties
of these sediments, the areas represented by samples 1, 2, and
11 being low in total organic carbon and nitrogen as well as
base-exchange capacity. These areas represent the coarser or
sandier sediments in the reservoir where the stream waters
with their incoming loads enter the main body of water in the
reservoir. From these locations on downstream to the dam the
sediments increase progressively in organic matter and nitrogen
as well as in total clay content. Sediments entering the reservoir
from the south, the region of sample 1, are much more alkaline
than are those entering from the west, the region of sample
11. The sediments are, in general, quite acid and low in
organic carbon and nitrogen indicating that they are not pre­
dominately surface soil materials.
The material accumulating in the reservoir is quite high in
fertility. During its accumulation farmers in the watershed
area have lost an equivalent of 5 tons of muriate of potash, 25
tons of superphosphate, and 40 tons of ammonium nitrate in
the form of available nutrients contained in the sediments from
the watershed. In terms of present-day prices of fertilizers, this
represents an annual loss of over $200 worth of fertilizers from
the watershed in the form of erosion.
The volume-weights, or densities, of the sediments vary with
location in the reservoir. Sediments from areas of rapid change
in the rate of flow of the incoming water, as represented by
samples 1, 2, 5, and 11, are sandier and higher in silt than are
the sediments from areas closer to the dam where the water
moves quite slowly. In the dam area the sediments are low in
volume weight and quite high in clay content. Therefore, con­
siderable sorting of sediments has occurred within the reservoir.
The rather high amounts of clay in the sediments represented
by samples 6 to 9 are indicative of the slow movement of water
through the main body of the reservoir.
5
Engineering News-Record March 20, 1952, p. 31, McGraw Hill Publications,
New York, N. Y.
U. S. DEPARTMENT OF AGRICULTURE
SOIL CONSERVATION SERVICE
HANCOCK COUNTY. ILLINOIS
R7W
CONSERVATION SURVEY LEGEND
CARTHAGE LAKE
HANCOCK COUNTY, ILLINOIS
SOIL GROUPS
14,14h M o d e r a t e l y Well Drained P r a i r i e Soils
18,34,15 Imperfectly D r a i n e d Soils
12,13 P o o r l y D r a i n e d P r a i r i e Soils
46 Well D r a i n e d T i m b e r Soils
16,20,17 P o o r l y Drained Claypan Soils
51 Bottomlands
LAND USE
L Cultivated Land
P P a s t u r e Land
H F a r m s t e a d s and Miscellaneous
EROSION
+
0
1
2
3
and +C Deposition
No A p p a r e n t E r o s i o n
Slight E r o s i o n
M o d e r a t e Erosion
Severe Erosion
SLOPES
A
B
C
D
E
Uncontrolled Conservation Survey Mosaic Compiled by the Cartographic Division,
Soil Conservation Service, Region III, Milwaukee, Wisconsin.
F r o m USDA A e r i a l Photographs RX " 1 9 3 8 " Hancock County, Illinois.
Conservation Survey by the Soil Conservation S e r v i c e .
Approximate Scale in Miles
0 to l½ P e r c e n t
1½ to 4 P e r c e n t
4 to 7 P e r c e n t
7 to 12 P e r c e n t
Over 12 P e r c e n t
FIGURE
11.
12
TABLE 4
Chemical and Physical Data on Lake Carthage Sediment Samples
Sample
Number
Volume
Weight
Total
Carbon
(%)
Total
Nitrogen
1.55
1.28
1.72
2.06
1.85
2.06
2.10
2.41
1.89
2.20
1.37
0.144
0.110
0.152
0.178
0.170
0.184
0.183
0.198
0.206
0.204
0.106
.
1
2
3
4
5
6
7
8
9
10
11
0.97
1.09
0.75
0.74
0.73
0.65
0.71
0.66
0.75
0.67
1.11
(%)
Exchange
Total
Capacity Exch'g'ble
m.e./100 m.e./100gm.
22.5
17.7
29.4
32.5
30.9
37.1
34.8
38.7
24.9
35.0
19.5
23.7
17.8
25.8
28.7
25.8
31.2
30.4
29.6
29.6
27.0
17.2
Origin of Sediment. The sediments entering the reservoir
seem tobe of two distinct types. Material coming in at the
south, as represented by sediment samples 1, 2, and 3, is quite
high in pH and indicates that uhweathered loess must-be en­
tering the reservoir along with surface soil. The somewhat
alkaline nature of this sediment suggests that sheet erosion and
the extension of existing small or shallow gullies working back
into the watershed are the primary sources of the sediments
entering at this point. Much of this material appears to be sur­
face soil and unweathered loess.
Sand
Silt
Clay
pH
(%)
(%)
(%)
6.3
6.0
5.4
5.7
5.1
5.2
5.2
4.8
5.2
4.9
5.4
0.8
1.1
0.1
0.1
0.3
0.1
0.1
0.1
0.2
0.1
2.9
63.4
63.6
53.8
48.2
49.8
40.0
42.2
34.4
43.7
61.4
64.7
28.7
25.2
38.6
44.0
44.7
54.0
50.6
59.7
49.9
30.3
26.7
Available Available
Potassium Phosphorus
lbs./acre lbs./acre
300 +
300 +
300 +
300 +
300 +
300 +
300 +
300 +
300 +
300 +
300 +
200 +
200 +
200 +
. 200 +
200 +
200 +
200 +
200 +
200 +
200 +
200 +
In contrast, the sediments entering from the west, as repre­
sented by samples 5 and 11, are quite acid in character. Since
these sediments are more acid than the normal surface soil and
considerably more acid than the unweathered loess, they must
be coming from the deeper more acid and weathered Illinoian
till which is found below the loess: In this area of the watershed
gully erosion extending down into the weathered Illinoian till
appears to be an important source of sediment accumulating
in the reservoir. Sediment control in the reservoir appears to
involve the control of both sheet and gully erosion in the
watershed.
WATERSHED
INTRODUCTION.
. Many watershed factors affect the rate of sedimentation of
reservoirs. They include size of drainage area, topography, soil
types, slopes, and land use. The.sources of sediment must be
determined if an effective sediment control program is to be
developed for the reduction of reservoir damages. Further­
more, the relative importance of the watershed factors must
be examined in order to develop reservoir design data.
PHYSIOGRAPHY
The watershed of Lake Carthage lies entirely within Hancock
Country Illinois. Lake Carthage was built on a tributary of
Long Creek in Section 13 Township 5 North, Range 7 West.
Total watershed area is 2.90 square miles.
The watershed of Lake Carthage is located in the west cen­
tral portion of the Galesburg Plain,6 a minor division of the
Central Lowland Province. It consists of a level to undulatory
till plain in a late youthful stage of geologic erosion.
SOIL GROUPS
The soils of the watershed were divided into six groups.
There are three basic groups of soils in the watershed, upland
prairie soils, upland timber soils and bottomlands. However,
since there is no woodland in the watershed at the present time,
a soils grouping was formulated to combine soils of similar land
use capabilities rather than soils of similar origin.
B
Leighton, M. M., Ekblaw, George E., and Horberg, Leland. Physiographic
Divisions of Illinois. Illinois Geological Survey, Report of Investigations
No. 129, 33 pages, illus.,Urbana, Illinois, 1948.
The conservation survey map of the watershed is shown in
Figure 11. The largest groups of soils are the Virden and
Herrick silt loam groups (Poorly Drained Prairie) as shown on
Table 5. The Herrick silt loam group is the most extensive soil
in the watershed, occupying 63.5 per cent of the area. Imper­
fectly drained soil groups mapped as Velma, Blair and ClintonMottled phase, silt loams, occur on 15.7 per cent of the area.
The moderately well drained prairie soils (Harrison silt loam
groups) occur on 15.6 per cent of the area. Poorly drained claypan soils (Berwick, Whitson and Dunkel silt loam groups)
occur on 1.5 per cent of the area as do the well drained timber
soils (Hickory gravelly loam group). Bottomlands (Huntsville
loam and associated groups) occupy 1.9 per cent of the water­
shed.
In general the dark prairie soils are more fertile than the
light-colored timber soils. The relative productivity of soils in
Lake Carthage Watershed may be found in Table 6.
SLOPES
Slopes influence the velocity of runoff and its ability to erode
soil. In general, slopes are not steep in the Lake Carthage
Watershed in comparison with watersheds of similar size in
other parts of the state. From Table 7, it is calculated that 79.4
per cent of the watershed area has less than 4 percent slope.
The degree of slope in any part of the watershed is related to
the extent of development of the drainage system. The upland
areas are level to gently sloping (A slopes). The gentle slopes
of the upland area drop off into moderately sloping waterways
and the side slopes of the waterways become progressively
steeper as they approach the stream. The maximum steepness
13
PRESENT LAND USE
occurs along the valley sides of the main streams and en­
trenched tributaries. Of the total cropland in the area 93.3
per cent is located on slopes of less than 4 per cent. About 38.0
per cent of the pasture land is located on slopes of less than 4
per cent as shown in Table 9.
One of the more important factors that affect the rate of
sediment production is land use. Three classes of land use,
cropland, pasture and miscellaneous, were mapped in the con­
servation survey. Cropland is all land on which crops were
grown at the time of the survey. It includes land in row crops,
small grains and hay. Pasture is land in perennial grasses. Mis­
cellaneous land consists of land used for farmsteads, roads or
other purposes.
Land use in general is related to soil groups. Thus 98.6 per
cent of the cropland in the watershed is located on soil groups .
1, 2, and 3 (See Table 8). Cropland is confined primarily (93.3
per cent) to A and B slopes while pasture is fairly well dis­
tributed on all slopes. (See Table 9).
Table 10 presents a general summary of the capability of
the lands of the watershed as compared to the present use of
these lands. This shows that 86.6 per cent of the watershed is
in land capability classes I, II and III which is considered safe
for continuous cultivation. At the time of the survey, 98.1 per
cent of the cultivated land falls within these classes.
Table 10 also shows that 9.4 per cent of the watershed area
is in land capability classes VI and VII (not recommended for
cultivation). Class IV land which can be cultivated only 1
year in 6 occupies 4.0 per cent of the area. Only 1.4 per cent
of the land now being cropped in the watershed is class IV land.
Table 11 shows the land use history in Prairie Township.
TABLE 5
Acreages and Percentages of Various Soil Groups in
Carthage Watershed, Carthage, Illinois
Soil Group
Area
(acres)
Moderately Well Drained Prairie
Harrison Silt Loam Group
Imperfectly Drained Soils
Velma Silt Loam Group
Blair Silt Loam Group
Clinton-Mott Phase Silt Loam Group
Total
Poorly Drained Prairie
Virden Silt Loam Group
Herrick Silt Loam Group
Total
Moderately Well Drained Timber
Hickory Gravelly Loam Group
Poorly Drained Claypan Soils
Berwick Silt Loam Group
Whitson Silt Loam Group
Dunkel Silt Loam Group
Total
Bottomlands
Huntsville Loam Groups
Entire Watershed
(per
cent)
300.3
15.6
16.3
194.1
92.6
0.9
10.0
4.8
303.0
15.7
8.5
1227.3
0.4
63.5
1235.8
63.9
28.9
1.5
14.1
13.5
1.6
0.7
0.7
0.1
29.2
1.5
35.5
1.9
1932.7
100.0
EROSION
General. Two kinds of water erosion occur in the watershed:
sheet erosion and channel erosion. In developing any type of
watershed treatment program for protection of a reservoir, it is.
of primary importance to know where sediment is coming from
and how much of the sediment is actually getting down to the
reservoir.
The degree of erosion that has taken place in the watershed
was mapped by comparing the thickness of different soil layers
with that of similar soils and slopes in locations protected from
erosion. The following erosion groups were mapped:
No apparent erosion: Approximate original depth of
topsoil still remains.
Slight to moderate erosion: Over seven inches of
original topsoil remaining, no subsoil exposed by plow.
TABLE 6
.
Estimated Crop Yields in Carthage Watershed As Related to Soils
Soils
1. Moderately Well Drained Prairie Soils
Per cent
Watershed
15.6
2. Imperfectly Drained Soils
15.7
3. Poorly Drained Prairie Soils
63.9
4. Well Drained Timber Soils
5. Poorly Drained Claypan Soils
1.5
1.5
6. Bottomlands
1.9
1
Manage­
ment
System
Good
Fair
Good
Fair
Good
Fair
Good
Fair
Average Yields Bushels per Acre*
Corn
Wheat
Oats
Soybeans
62
57
51
45
69
62
N
50
41
D
23
24
22
21
28
23
N
22
18
D
36
45
42
44
37
N
36
32
D
24
24
26
23
26
23
N
20
17
D2
Not adapted.
Subject to high risk from flooding.
*Crop yields were estimated from data in Illinois Agricultural Experiment Station, Bulletin No. 522, entitled, "How Productive
Are the Soils of Central Illinois" by R. T. O'Dell.
2
14
TABLE 7
Distribution of Slope Classes in Each Soil Group
Soil Group
1.
2.
3.
4.
5.
6.
Moderately well drained prairie
Imperfectly drained soils
Poorly Drained Prairie
Well drained timber soils
Poorly drained claypan soils
Bottomlands
TOTAL
B Slopes
l½-4%
A Slopes
0-1½%
(acres)
30.2
(%)
2.3
1235.8
94.2
11.3
35.5
.8
2.7
1312.8
(acres)
166.6
41.9
C Slopes
4-7%
(%)
73.6
18.5
17.9
7.9
100.0 .226.4
100.0
(acres)
103.5
70.1
D Slopes
7-12%
(acres)
(%)
59.4
40.2
.7
0.4
174.3
100.0
79.1
(%)
100.0
E Slopes
Over 12%
(acres)
300.3
79.8 303.0
1235.8
20.2
28.9
29.2
35.5
(acres)
(%)
111.9
28.2
79.1
100.0
Total
100.0 1932.7
140.1
TABLE 8
Distribution of Present Land Use in Each Soil Group
Soil Group
1.
2.
3.
4.
5.
6.
Pasture
Cropland
Moderately well drained prairie
Imperfectly drained soils
Poorly drained prairie
Well drained timber soils
Poorly drained claypan soils
Bottomlands
TOTAL
Miscellaneous
(acres)
187.7
68.6
1156.2
1.7
18.5
(%)
(acres)
107.6
227.7
61.9
27.2
10.7
35.5
(%)
13.1
4.8
80.7
0.1
1.3
1432.7
100.0
470.6
100.0
22.8
48.4
13.2
5.8
2.3
7.5
(acres)
5.0
6.7
17.7
29.4
Total
(%)
17.0
22.8
60.2
100.0
(acres)
300.3
303.0
1235.8
28.9
29.2
35.5
1932.7
TABLE 9
Distribution of Present Land Use in Each Slope Class
Slope Class
A
B
C
D
E
(0-1½ per cent)
(1½-4 per cent)
(4-7 per cent)
(7-12 per cent)
(Over 12 per cent)
TOTAL
Cropland
Miscellaneous
Pasture
Total
(acres)
1187.0
149.4
72.7
20.4
3.2
(%)
82.9
10.4
5.1
1.4
.2
(acres)
107.0
72.0
98.2
57.2
136.2
(%)
22.7
15.3
20.9
12.2
28.9
(acres)
18.8
5.0
3.4
1.5
0,7
(%)
63.9
17.0
11.6
5.1
2.4
(acres)
1312.8
226.4
174.3
79.1
140.1
(%)
67.9
11.7
9.0
4.1
7.3
1432.7
100.0
470.6
100.0
29.4
100.0
1932.7
100.0
Moderately severe erosion: Occasional to frequent
exposure of subsoil by plow, three inches to seven
inches of topsoil remaining.
Severe erosion: Erosion of the subsoil, less than three
inches of surface soil remaining.
Very severe erosion: Frequent gullies, too deep to
cross with farm implements and very severe erosion
that has penetrated into parent material.
Erosion by sheet wash and erosion by channel flow were
mapped separately during the course of the conservation survey, as was deposition on fioodplains and in channels.
No apparent erosion has occurred on 63.2 per cent of the
watershed. Slight to moderate erosion has occurred on 28.8 per
cent and moderately severe erosion on 7.4 per cent of the watershed. Severe erosion has occurred on 0.6 per cent of the watershed. Severe and moderately severe erosion has occurred on
soils of groups 1, 2 and 4. (See Table 12)
The distribution of erosion in relation to slopes is shown in
Table 13. Slight to moderate erosion has occurred on all slopes
with the largest percentage on B slopes. Moderately severe
and severe erosion has occurred on B, C, D, and E slopes,
while very severe erosion is confined to C, D, and E slopes.
Figure 12 shows on eroded permanent pasture in the drainage
area. Figure 13 shows a badly eroded feedlot.
The volume of sediment that is being produced at the present time by sheet erosion can be computed directly from the
physical land conditions and cropping patterns which exist in the
watershed. This method is based on available research data.
The basic data for computing damage from sheet erosion
consists of the following:
a. Annual soil losses in tons per acre for soil with an erodibility factor of 1.0, under continuous corn, with and without conservation practices for various per cent and length
of slopes.
b. Factors for computing the effects of cropping patterns and
soil types on soil losses.
15
TABLE 10
Land Use Capability Classes Compared With Existing Land Use
Cropland
(acres)
Class I'Land
Suitable for cultivation, requir­
ing no erosion control practices
to maintain soil for general agri­
cultural practices
Class II Land,
Good land that can be cultivated
safely with easily applied prac­
tice.
Class III Land
Moderately good land that can
be cultivated safely with such in­
tensive treatments as terracing
and strip cropping
Class IV Land
Best suited to hay or pasture, but
can be cultivated occasionally,
usually not more than 1 year in 6
Class VI Land
Not recommended tor cultiva­
tion. Best suited for permanent
pasture
Class VII Land
Not recommended lor cultiva­
tion. Suited for woodland or pas­
ture with major restrictions in use
TOTAL
(%)
(acres)
Total
Miscellaneous
Pasture
(%)
(acres)
(%)
(acres)
(%)
1177.6
82.2
69.6
14.8
18.8
63.9
1266.0
65.5
149.7
10.4
65.1
13.8
5.0
17.0
219.8
11.4
78.6
5.5
106.3
22.6
2.8
9.5
187.7
9.7
19.5
1 .4
65.4
12.0
2.1
7.2
78.0.
4.0
7.3
.5
70.3
36.2
.7
2.4
178.3
9.2
2.9
0.6
2.9
0.2
470.6
100.0
1932.7
100.0
Other
Crops
Plowland
Idle or
Failure
1432.7
100.0
29.4
100.0
TABLE 11
Land Use, Prairie Township, Hancock County, Illinois 1938-491
Per cent of Cropland In:
Acres per Farm
Year
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
Av. 1942-45
Av. 1946-49
12-year Av. 1938-49
1
Number
of
Farms
142
137
138
141
137
126
129
120
115
116
111
122
128
116
128
Total
138
142
147
143
151
164
152
167
171
178
170
157
158
169
155
Based on assessor's census of farm acreage.
Cropland
115
116
119
112
120
129
128
124
123
122
126
118
125
122
121
. Corn
32
30
27
30
28
33
34
30
38
34
40
40
31
38
33
Soybeans
Small
Grain
Hay
16
22
21
23
17
31
32
40
31
36
22
19
32
27
27
28
24
20
23
28
16
9
17
20
17
28
32
15
24
21
23
22
30
21
24
18
22
13
11
13
10
9
20
11
18
1
1
1
2
2
3
2
1
3
2
1
16
TABLE 12
Distribution of the Erosion Group in Each Soil Group
Soil Group
1.
2.
3.
4.
5.
6.
Moderately well drained prairie
Imperfectly drained soils
Poorly drained prairie
Well drained timber soils
Poorly drained claypan soils
Bottomlands
TOTAL
No Apparent
Erosion
(acres)
7.7
(%)
1176.1
96.4
1.6
35.5
0.1
2.9
1220.9
100.0
0.6
Silght to
Moderate Erosion
(acres)
224.2
228.0
59.7
16.9
27.6
(%)
556.4
100.0
40.3
41.0
10.7
3.0
5.0
Moderately
Severe Erosion
(acres)
68.4
63.4
(%)
Severe Erosion
(acres)
(%)
47.8
44.3
11.6
94.3
11.3
7.9
.7
5.7
143.1
100.0
12.3
100.0
Total
(acres)
300.3
303.0
1235.8
. 28.9
29.2
35.5
1932.7
TABLE 13
Distribution of Erosion Groups in Each Slope Class
Slope Group
A
B
C
D
E
(0-1½ per cent)
(1½-4 per cent)
(4-7 per cent)
(7-12 per cent)
(Over 12 per cent)
TOTAL
No Apparent
Erosion
(acres)
1220.9
1220.9
(%)
100.0
100.0
c. The cropping pattern and the total acreage in each soil
group by per cent and length of slope and degree of
erosion.
The annual soil loss ("a" above) multiplied by the appro­
priate cropping pattern factor and soil factor, gives the annual
soil loss in tons per acre. This loss, converted to acre-inches
and multiplied by the acreage on which it occurs, gives the
annual volume of sediment in acre-inches produced by this
source.
Table 15 presents a summary of above computations which
indicates that under present practices (without an applied
conservation program) the soil loss from sheet erosion amounts
to 7,343 tons per year. Assuming a weight of 1,800 tons per '
acre-inch, this loss amounts to 4.08 acre-feet per year.
Gully Erosion. In order to estimate the importance of gullies
as a sediment source and also as a destructive agent to farm
operations in the Carthage Reservoir Watershed, a particular
effort was made to locate, measure, and describe every gully.
All gullies that could not be crossed with conventional farm
machinery were studied by the conservation surveyor in the
field. The location of the gully and measurements thus deter­
mined were recorded on a transparent overlay on the aerial
photograph.
Thirty-six gullies were located and described, the largest
being 15 feet deep, 20 feet wide and 825 feet long. This single
gully in its lifetime has produced over 6 acre-feet of sediment
and has made void over one-third acre of land. It was possible
to locate the head of twenty of the gullies on aerial photographs
taken in 1938. By pinpointing the head of the gully at its 1938
location and its 1949 location, an accurate measurement of the
growth in length of the gully was obtained. Sixteen of the gully
heads could not be accurately located on the 1938 photos, be­
ing, in many cases, obscured by brush or trees.
Slight to
Moderate Erosion
(acres)
91.9
219.4
75.6
46.8
122.7
556.4
Moderately
Severe Erosion
(acres)
Severe Erosion
(acres)
Total
16.5
39.4
13.6
8.4
22.1
7.0
94.2
27.4
14.5
4.9
65.8
19.1
10.2
4.5
4.9
2.9
36.6
39.8
23.6
(acres)
1312.8
226.4
174.3
79.1
140.1
100.0
143.1
100.0
12.3
100.0
1932.7
(%)
(%)
(%)
The length of growth since 1938 and present cross-sectional
areas indicate that a volume amounting to 137,391 cubic-feet
of material has been removed from the twenty gullies since
1938 by head growth.
Assuming that the twenty observed gullies are an accurate
sample, the following is evident:
137,391 cubic feet = amount from 20 gullies in 11 years.
22,482 cubic feet = amount per year by head growth of all
gullies.
The area damaged by headward growth of gullies was com­
puted by the same process. The twenty gully sample indicates
that 44,965 square feet of land surface has been voided by this
growth. The total area is computed:
The average annual area = 7,357 square feet, or 0.17 acre.
Uncontrolled gullies grow wider, deeper and longer. Accurate
records of gully widths and depths in the past are not available
in the Carthage area. In order to estimate accurately the total
volume of sediment produced and the area affected by gullies,
a number of detailed gully growth studies have been made by
the Soil Conservation Service. In the Missouri Basin Loess
Hills (where soil materials and topography are similar to those
at Carthage) these studies7 indicate that "head growth" repre­
sents approximately 64 per cent of the volumetric growth
and 62 per cent of the areal growth of these type of gullies.
By applying these percentage factors, the following estimates
were derived for the watershed above Carthage reservoir.
Gullies produce 35,128 cubic-feet (0.81 acre-foot) of sediment
and 11,866 square feet (0.27 acre) of surface are voided an­
nually.
7
Unpublished data. U.S.D.A. Soil Conservation Service. Milwaukee, Wisconsin.
17
Sources of Sediment. The watershed study indicates that sheet
erosion is producing an estimated 4.08 acre-feet of sediment
and gully erosion an additional 0.81 acre-feet of sediment
each year. Roadside ditches and streambank erosion are
estimated to produce approximately 0.1 acre-foot annually.
At the present time the 96.3 acres of C, D and E slopes which
are cultivated produce an estimated 3,738 tons of sediment from
sheet erosion each year, compared to 3,605 tons originating
from sheet erosion on the remaining 1,836 acres in the water­
shed. It is interesting to note that these critical areas produce
sediment at an estimated rate of approximately 39 tons per
acre per year compared to approximately 2 tons per acre per
year from the less critical areas.
The various types of erosion in the watershed produce ap­
proximately 5.0 acre-feet of sediment annually. The annual
Although volumetric data were not obtained, survey notes
were made to indicate that uncontrolled streambank erosion
is taking place at the numerous bends of the stream above the
lake.
Erosion of roadside ditches, while a minor sediment source,
contribute to the action of several major gullies. These road­
side ditches should be controlled as part of a waterway stabili­
zation program.
From Table 11 it can be computed that 78 per cent of the
farm land is used for crops. Since 86.6 per cent of the area is
safe for continuous safe cultivation, it is obvious that major
reductions in cultivated acreage will not be necessary. The
conservation survey data shown in Table 14, indicate that a
large per cent of the moderate and severe erosion was found in
pastures.
TABLE 14
Distribution of Erosion Groups in Each Land Use Class
Land Use Class
Cropland
Pasture
Miscellaneous
TOTAL
No apparent
Erosion
Slight to
Moderate Erosion
Moderately
Severe Erosion
Severe Erosion
Total
(acres)
1107.9
95.3
17.7
(%)
90.7
7.8
1.5
(acres)
235.2
312.4
8.8
(%)
42.3
56.1
1.6
(acres)
82.3
58.5
2.3
(%)
57.5
40.9
1.6
(acres)
7.3
4.4
.6
(%)
59.3
35.8
4.9
(acres)
1432.7
470.6
29.4
1220.9
100.0
556.4
100.0
143.1
100.0
12.3
100.0
1932.7
TABLE 15
Estimated Reduction in Sheet Erosion Annually From a Watershed Treatment Program
Lake Carthage
Tons of Soil Lost
Without Program
Slope
Cultivated
(acres)
A
B
C
D
E
1,187
149.4
72.7
20.4
3.2
Tons/Acre
2.0
6.7
31.0
63.0
79.0
Subtotal
Total Tons Lost
Tons Lost
2,374
1,000
2,245
1,265
238
Pasture
(acres)
125.8
77.0
101.6
58.7
136.9
Tons/Acre
0
.4
.6
.6
.6
7,132
Tons Lost
0
31
61
35
84
211
7,343
With Recommended Program
Slope
A
B
C
D
E
Subtotal
Total Tons Lost
Cultivated
(acres)
1,187
149.4
72.7
Tons/Acre
1.0
3.0
4.0
Tons Lost
1,187
448
289
1,924
Total soil loss reduced 72.8 per cent due to watershed program.
Pasture
(acres)
125.8
77.0
101.6
79.1
140.1
Tons/Acre
0
.1
.2
.2
.2
Tons Lost
0
8
20
16
28
72
1,996
18
accumulation in the lake is only 4.19 acre-feet. The difference
of about 0.8 acre-foot is assumed to be deposited in colluvial
areas, on floodplains, and in channels upstream from the lake,
and to pass over the dam in suspension.
CONSERVATION
Land use adjustments and conservation practices are needed
in the watershed both to develop a more permanent and profit­
able agriculture and to reduce the rate of sedimentation in
Lake Carthage.
Lake Carthage has a relatively small watershed. Only one
conservation plan is in operation in the watershed, and one
plan is in the farm planning stage. Relatively good rotations
have been used on much of the cropland in the reservoir water­
shed. The legume acreage has not been up to the standards of
land use capability requirements nor up to a desired level.
Clover stands are sparse in some instances and would be much
better if the soil were tested and the proper amounts of lime­
stone and fertilizer were applied.
Only two farms in the watershed have any contouring. Sheet
erosion and runoff of the water occur on corn and soybean fields
and small grain fields which are planted up and down the hill.
Most of the crop fields do not have steep slopes. Some of the
present cropland should be in permanent pasture. The land use
pattern could stand considerable improvement.
The present permanent pastures need improvement. Soil
treatment, including applications of limestone, phosphate, and
potash, is needed. Reseeding and renovation are also needed
on many of the pastures. In many instances brush should be
grubbed out and trees and hedge in the permanent pastures
should be removed. Very few of the permanent pastures are
mowed, and in general they are weedy. The permanent pastures
are probably less than 50 per cent as productive as could rea­
sonably be expected. Many of them are only exercise lots,
particularly during the summer months. It is quite apparent
that alfalfa-brome grass is suitable in this area. In a few in­
stances some of the present area in permanent pasture might
better be in trees; livestock, of course, should be kept out
of these wooded areas.
The waterways in much of the watershed should be shaped,
treated according to soil test and seeded. Some of the draws
should be planted to trees and livestock fenced out. Numerous
drop boxes and some soil-saving dams are needed in the water­
ways leading to the reservoir.
RESULTS
CAUSE OF HIGH RATE OF STORAGE LOSS
Watershed Factors. The average annual sediment accumula­
tion in Lake Carthage amounts to 4.19 acre-feet, as shown by
the survey. From studies in reservoirs where both sediment
accumulation and sediment discharge were obtained, it is esti­
mated that this reservoir has a trap efficiency of 93 per cent.
It follows then that an average of 4.50 acre-feet of sediment is
being produced on the watershed; 4.19 acre-feet remaining in
the reservoir and 0.31 acre-feet going over the spillway.
As indicated in previous paragraphs, 0.81 acre-feet of sedi­
ment (18 per cent of the total) is being produced each year
from gullies.
It is estimated that sediment originating from sheet erosion
makes up the bulk of the sediment, probably about ± 3.60
acre-feet per year.
Sediment from streambanks, bottomland scour, and road­
side ditches is a minor part of the total.
REMEDIAL MEASURES
Practicability. The need for action regarding the water
source for Carthage has been shown earlier in this report in
Figure 10. It is seen that some action will be necessary soon to
avert a possible water shortage within the next four years.
Action is needed to safeguard the city against droughts which
can be expected to concur at much greater recurrence intervals,
possibly once in 25 or once in 50 years. Figure 10 shows that
the application of a watershed conservation program will not
protect the lake from a water shortage till the year 1975, and
the effect would be relatively small at that time. A serious
shortage could occur in any year. Lake Carthage is now inade­
quate to serve the growing community and the water supply
must be augmented in some way. Consequently early considera­
tion should be given to possible remedial measures before a
shortage occurs.
Raising the Dam. One of the first steps usually considered
by lake owners in increasing storage capacity is the raising of
the spillway and possibly the entire dam. Such action is usually
subject to limitations because the original dam and spillway
were probably designed to give the most economical project
available at that site. Limited increase in storage space can
often be gained in this manner and such action should be con­
sidered.
Other Lakes. In searching for additional storage space, addi­
tional reservoir sites should be considered. In past studies,
reservoir sites on Long Creek and the Lamoine River have been
investigated and possibly the development of additional sur­
face storage capacity at one of these sites should be given con­
sideration at the present time.
Dredging. Reservoir owners faced with a sedimentation prob­
lem sometimes resort to dredging to remove the sediment and
regain storage space. The unit cost of dredging is normally high
in comparison to other methods of regaining or providing addi­
tional storage. Dredging has proven to be worthwhile in some
cases where deltas of sediment or local shallows have formed
within the lake which ruined the aesthetic properties of the
lake.
The City of Macomb has recently carried out dredging opera­
tions to remove sediment from their municipal reservoir.
Vegetative Plantings. In some cases on record sedimentation
in a reservoir has been partially relieved by the introduction
of thick growing vegetative screens into the delta areas in the
upper part of the lake. The total effect of such planting however
in reducing the total volume of sediment reaching the reservoir
can be considered minor in comparison to a program ot erosion
control covering the entire watershed. Proper soil treatment,
adequate crop rotation, and a sound pasture renovation and
management program are essential in this watershed to control
soil movement. The planting of trees and shrubs in particular
areas suited for woodland or wildlife is highly desirable. The
local Farm Adviser or Soil Conservation District personnel
should be consulted for the best location of such plantings and
the species to be planted.
WATERSHED TREATMENT PROGRAM
Needed Measures. One of the methods of affecting a per­
manent reduction in the rate of sediment inflow to Lake Car­
thage is the establishment of an intensive land treatment pro­
gram on the watershed to control sheet erosion on the farmland.
Because of the seeming feasibility of establishing such a con­
servation program on the Lake Carthage Watershed, an in-
19
FIG. 12. ERODED PERMANENT PASTURE IN WATERSHED. No
Soil Treatment, Poor Stand and Negligible Production, Feed Lot
on Slope in Background.
vestigation has been made of the elements of such a program
and the possible benefits.
By study of the conservation survey data, it is possible to
estimate the annual soil loss from sheet erosion in this water­
shed and the probable reduction that can be accomplished
under a land treatment program.
The most striking fact revealed by the conservation survey
data is that more than one-half of the sediment produced to
date in this watershed has originated from areas now used for
pastures. When it became uneconomical to grow crops on the
steeper slopes they were "retired." Apparently little thought
has been give to the potential pasture thus attained, nor effort
expended to more effectively utilize these areas by seeding,
fertilizing, mowing, etc. to gain the potential yields thus
available.
The major recommended change in land use is the conversion
of 23.7 acres of cultivated land on D and E slopes to permanent
pasture or hay. The crop rotations now being followed in the
watershed cannot be considered adequate either to maintain
production or stabilize soil. Prom Table 15 it is evident that the
72.7 acres of C slope now in cultivation produce nearly as
much sediment as 1,187 acres of A slope. Contour cultivation
with supplementary soil and water conservation practices,
such as diversion ditches and terraces, are needed badly for
these areas. The more nearly level area, A and B slopes, should
be farmed in accordance with its use capability. This would
require more legumes and close growing crops than are used
at the present time.
Structures. In order to control the velocity of the runoff
water in the gullies, structures may be needed. The Soil Con­
servation Service has found pipe drop inlet spillways to have
the advantage of construction economy and efficiency of opera­
tion in this area. Structures accomplish two objectives, (a) con­
trol head growth, and (b) control the velocity of the run-off
water so that vegetation can be established to stop the gullies
from growing deeper and wider.
Incidental to the control of gullies, but a tangible benefit, is
the farm pond sometimes created above the structure. Properly
designed, these ponds will have the effect of stablizing the run­
off, as well as augmenting the local water supply.
Probable Present Annual Soil Loss. Table 15 shows the
estimated amount of soil lost from the watershed each year
under present land use practices. Under present conditions,
the total soil loss from sheet erosion is calculated to be 7,343
tons per year. To establish this estimate, a review was made
of the land use followed during the past four years (1946-1949).
This showed that a rotation of corn, corn, corn, small grain,
and hay (3-1-1) was followed on 65 per cent of the area; corn
or soybeans—small grain with a sweet clover catch crop on
26 per cent of the area; and straight corn on 9 per cent of the
area. Soybeans are substituted for corn in over half of the
above rotation. Soil losses from steep pasture was estimated to
be 0.6 tons per acre per year. This is a very high estimate, but
is justified by the poor cover found on the pastures and the
numerous paths and trampling.
Probable Soil Loss Under Proposed Program. Table 15 shows
that the present annual soil loss, from sheet erosion, 7,343 tons,
could be reduced to approximately 1,996 tons, or 72.8 per cent.
The program recommended to bring about such a reduction is
based on standard land use capability recommendations and
slope-practice data of the Soil Conservation Service.
The amount of reduction of sediment reaching the lake
achieved by the adaption of soil conservation practices will de­
pend on the completeness of application. There is little question
that the changes in land use that are recommended to bring
these areas within the recommended use according to their
capability is practical. Referring to Table 10, it can be seen that
the 26.8 acres of land, now cultivated, that are recommended
for pasture would be easily offset by using part of the 134.7
acres of Class I and II land now in pasture for cropland.
The economic advantages to the farmer of the use of con­
servation practices is becoming known in the area and their
early adaption and widespread use is anticipated.
Reduction of Sediment Reaching Lake. Since sheet erosion
is credited with 82 per cent of the total sediment in the reser­
voir, the reduction by 72.8 per cent thus achieved will result in
a 59.7 per cent reduction of the sediment entering the reservoir.
Gullies produce an estimated 16 per cent of the total sedi­
ment entering Lake Carthage. For the purpose of further analy­
sis of the effects of a watershed treatment program, it is esti­
mated that with a reasonable amount of control, soil loss from
this source can be reduced by one-half. This reduction would
result in an 8.0 per cent (16 per cent x 50 per cent) reduction
in the sediment reaching the lake. No reduction is anticipated
in the approximately 2 per cent of the sediment which is de­
rived from other sources.
The combination of the 59.7 per cent reduction by land treat­
ment, and the 8.0 per cent reduction by gully stabilization will
effect a total reduction of 67.7 per cent of the sediment inflow
FIG. 13. CATTLE IN BADLY ERODED FEEDLOT ON STEEP SLOPE
DRAINING DIRECTLY INTO LAKE CARTHAGE. Manure,
Soil Are Washed into the Lake With Every Rain.
20
into the lake. The rate of storage loss would thus be reduced
from 1.03 per cent to 0.32 per cent per year. The volume of
sediment reaching the reservoir each year would be reduced
from 4.99 acre-feet to 1.61 acre-feet; 1.35 acre-feet of which
would be retained in the reservoir.
Extension of Life of Lake. The effect of this 67.7 per cent
reduction of sediment inflow into the lake is shown on the
graphs in Figures 9 and 10 earlier in this report, It is noted from
Figure 10 that the soil conservation program even though
initiated in the watershed at the present time would have no
great effect in protecting the lake against sediment accumula­
tions until about the year 1970 when the effectiveness of the
reduced sedimentation would be significant.
This does not mean that the rate of sedimentation could
not be reduced until 1970. For use in Figure 10, it is estimated
that if such a conservation program were begun in the year
1953 it could be completed in the year 1958 and that the entire
67.7 per cent reduction would take effect in the year 1958. In
Figure 10 the increase in total water consumption in future
years is the controlling factor causing the water shortage to
occur. In this case even though sedimentation in the lake were
reduced by this percentage, the shortage would nevertheless
occur.
In Figure 9 of this report has been shown the decrease in
reservoir capacity under the present rate of sedimentation. In
Figure 9 has also been plotted the reduction in rate of sedi­
mentation in future years if the above described watershed
treatment program were installed and were to take effect in
the year 1958. It is evident from Figure 9 that the installation
of such a conservation program will reduce the actual rate of
loss of capacity in the lake. Thus the ultimate life of Lake
Carthage will be increased considerably even though the use­
ful life of the lake may not be increased to a significant degree.
For this reason as well as the benefit to the land itself, the City
should consider means of bringing about the application of
this watershed program:
The conservation measures needed in this watershed are
measures similar to those needed throughout Hancock County
as well as the entire state and nation to provide for a more
permanent and productive agriculture. The Hancock County
Soil Conservation District has as its objective the application
of these measures within the county. Technical assistance is
given the District by the Soil Conservation Service, Extension
Service and other federal and state agencies. The District is
authorized to accept aid from any source in carrying out its
program. Efforts of the City Water Department to establish a
watershed treatment program could very reasonably be carried
out through this District.
The City of Decatur, faced with a serious reservoir sedimen­
tation problem, has maintained for many years a trained con­
servationist to work only on the reservoir watershed. This
man, paid entirely from city funds, gives technical help to
farmers in the area in a manner similar to that furnished all
farmers by the soil conservation district and the Soil Conserva­
tion Service. The City of Springfield maintains its own nursery
for furnishing seedlings lor planting on city-owned property
around Lake Springfield. The City of Macomb is aiding the
local soil conservation district in an increased effort to apply
needed conservation measures on the city reservoir watershed.
Many cities within the country have found it economical
to purchase all or much of the reservoir watershed for control.
In this manner the city water department can make certain
that the control of soil loss is complete. This does not mean that
the land is all taken out of cultivation or agricultural use. Such
lands are frequently leased to private interests for farming in
line with the capabilities of the land. As has been shown, much
of the land in the Lake Carthage watershed is suitable for
grassland. After purchase, and proper treatment, this land
could be leased for pasture. Such programs of watershed con­
trol have been found self-supporting and even profitable to
the city in many cases8. The City ot Akron, Ohio, has carried
on such operations profitably.
COSTS AND BENEFITS OF CONSERVATION
The Carthage Lake watershed consists of 1,933 acres. At
the time of the survey, conservation practices had been applied
on relatively little of the area. The adoption of a complete
plan of soil and water conservation and erosion control on all
the land in the Lake Carthage watershed would pay the farm­
ers in the long run. It would also very materially reduce the
silting of the lake and greatly prolong its ultimate life.
Present Practices. Rotations on the cropland are more in­
tensive than recommendations based on land-use capability
data. For the 12-year period 1938-49, approximately 60 per
cent of the cropland was in intertilled crops (corn and soybeans),
21 per cent in small grains, 18 per cent in meadow and one
per cent idle. For the four years immediately preceding the
survey, 1946-49, 65 per cent of the cropland was in corn and
soybeans, 24 per cent in small grains and only 11 per cent in
meadow. Thus, while the long-time rotation was approximately
a three-one-one, and the past four years a six-two-one, the
recommended rotation would be approximately a two-one-two.9
The better rotation needed on the cropland also would require
the use of supporting practices such as grass waterways, con­
touring, terracing, etc. The land use in the Carthage Lake
watershed follows the pattern for the surrounding land area in
Hancock County which averaged for the five years 1945-49,
57 per cent of the tilled areas in corn and soybeans, 24 per cent
in small grains, 17 per cent in meadow and two per cent idle.
The recommended use of cropland for Hancock County, based
on land-use capability data, is 40 per cent in intertilled crops,
22 per cent in small grains, and 38 per cent in meadow.
Supporting practices on the cropland, that is, use of grass
waterways, contouring and terracing would help materially in
retarding runoff and the silting of the lake that comes from
sheet erosion. At the present time, most of the crops are planted
without regard to slope and considerable sheet erosion and
runoff occurs on corn and soybean fields planted up and down
the slopes.
Soil fertility treatment, that is, the application of limestone,
phosphate and potash in accordance with needs as shown by
soil tests, is an important first step in the establishing of a
conservation program in this area. While limestone and phos­
phate requirements have been met on approximately half of
the cropland, very little of the pasture land has been treated.
It is estimated that approximately 60 per cent of the land area
is in need of soil treatment. Adequate soil treatment would
result in better stands and growth of legumes and grasses, re­
sulting in not only increased forage production, but also re­
duced runoff and soil and water losses.
Costs of Conservation. The costs of applying conservation
to the land in the Lake Carthage watershed will depend on
measures used. If primarily vegetative methods are used, the
costs will be approximately $38.00 per acre, for the land that
has had no soil fertility treatment.10 Assuming that 40 per cent
8
LaDue, Wendell R., Reservoir Lands Pay Their Way—Balanced Use of
Reservoir Lands, Journal of American Water Works Association, Vol. 40,
No. 8, August, 1948.
9
The numbers refer to years of intertilled, small grain, and meadow, respec­
tively. The recommended two-one-two rotation thus is corn-corn or soybeansmall grain-meadow-meadow.
10
This assumes average per acre soil treatment of three tons of limestone,
three-fourths ton rock phosphate or its equivalent in superphosphate and
200 pounds potash. Soil fertility treatment would thus cost approximately
$32.00 per acre, while waterways, seedings, terraces, trees and shrubs would
cost an average of $6.00 per acre for the 1,933 acres in the watershed.
21
of the land area has had soil treatment, average per acre costs
of conservation by vegetative methods would be approximately
$25.00 per acre of the watershed.
There are 36 major gullies in this watershed. If structures
are used to control the velocity of runoff water in the gullies,
the costs of conservation will be increased. Gully control struc­
tures may be found to be essential in order to retard or prevent
silting of the lake, and if so, they would have to be a public
expenditure rather than a private or farm owner expenditure.
If a sound conservation farm plan were adopted on all of the
farms in the watershed, including (1) land use and crop rota­
tions in accordance with soil capabilities, (2) soil fertility treat­
ment in accordance with soil tests, (3) use of supporting prac­
tices where needed as waterways, contouring and terracing,
(4) the improvement of permanent pastures and use of rota­
tional grazing, (5) the fencing out of woodland and gullies and
the planting of trees and shrubs, (6) the relocation of feedlots
from sloping hillsides to more level areas, it is reasonable to
assume that the silting of Lake Carthage would be greatly
reduced.
Studies of costs and benefits of contour farming in this area
show that contour farming alone, contour strip cropping, and
terracing result in high crop yields and do not increase the over. all cost of farm operation. Corn, soybeans, oats and wheat
yields were increased 12, 13, 16, and 17 per cent, respectively,
from contouring. Labor, power and machinery costs per crop
acre averaged $1.58 lower (at 1945 prices) on the farms that
were farming on the contour.
Benefits of Conservation. Studies of farm records show that
the application of soil conservation measures can be justified
economically by the farmer himself because the increased
yields of grain and forage crops from conservation farming
result in increased farm income.
On a practical, tenant-operated, livestock and grain farm in
this area, on land similar to that in the Lake Carthage water­
shed, conservation farming has resulted in increased production
and net farm income. Operating under a livestock-share lease,
the landlord and tenant have shared in both the costs and bene­
fits of their conservation program. Approximately 70 per cent
of their farm is tillable. They use a five-year corn-corn and soy­
beans-small grain-alfalfa bromegrass-alfalfa bromegrass rota­
tion. Since completing limestone and phosphate applications
to correct basic deficiencies, they are spending approximately
$2.00 per acre per year for fertilizers etc. for maintenance and
improvement of the land. Before starting the conservation
program, their crop yields were about equal to the county
average. Now their corn is yielding 20 bushels an acre above
the county average and yields of their other crops have im­
proved accordingly. Their net farm income is averaging 10
per cent above the average of all farm-account keeping farms
in Hancock County.
Another example of land use, production and income before
and after a program ot conservation was adopted on an in­
dividual farm and covering a 10-year period shows that all
crops yielded only 94 per cent of the county average before the
program was started and increased to 114 per cent afterwards—
a gain of 20 per cent. This gain in yields from reducing the acre­
age of intertilled crops and increasing the acreage of legumes
and grasses, plus other recommended conservation practices,
brought an annual return of $696.00 more from grain crops or
$1,019.00 more from all crops for each 100 acres of cropland.
Long-time Economic Results of Conservation Farming. A
summary of 10 years of data on 80 high- and 80 low-conserva­
tion farms in Illinois shows increased earnings on the high-con­
servation farms resulted from the adoption of soil conservation
and fertility improvement practices and from the improvement
of the general level of the management of the farm. At 1945
prices, the 10-year average increases in earnings from the highconservation farms compared to low-conservation farms aver­
age $6.05 an acre. Capitalizing this increased income at five
per cent, the value of the land on the high-conservation farms
would be increased by $121.00.
Economics of Conservation. Results ot 16 years of research
show that conservation farming not only protects soil and water
resources, but also increases tarm production and income. Al­
though some conservation measures increase production the
first year, conservation plans do not necessarily increase earn­
ings immediately. Often a considerable amount of effort and
money must be expended before positive results are achieved.
If the land has been poorly handled in the past, several years
may be required to restore its productivity andearning power
to a satisfactory level. The long-time benefits of conservation
are certain, however.
RECOMMENDATIONS
It is recommended that the City of Carthage engage a quali­
fied professional engineer to investigate the adequacy of the
present water supply system to furnish the present and future
needs of the city and to report on the most economical method
for maintaining an adequate water supply.
It is recommended that the City of Carthage undertake im­
mediately the application of a watershed treatment program
on the drainage area of Lake Carthage to reduce sedimentation
and prolong the ultimate life of this lake and the length of time
it can be used for the public water supply. It is suggested that
this program be carried out by (1) financial assistance from
the City to a local Soil Conservation District for intensified
conservation efforts on this watershed or (2) purchase of the
watershed or much of the critical erosion area by the City for
application of the needed conservation measures.
REPORTS OF INVESTIGATIONS
ISSUED BY THE STATE WATER SURVEY
No. 1. Temperature and Turbidity of Some River Waters in Illinois. 1948.
No. 2. Groundwater Resources in Winnebago County, with Specific Reference to Conditions at
Rockford. 1948.
No. 3. Radar and Rainfall. 1949.
No. 4. The Silt Problem at Spring Lake, Macomb, Illinois. 1949.*
No. 5. Infiltration of Soils in the Peoria Area. 1949.
No. 6. Groundwater Resources in Champaign County. 1950.
No. 7. The Silting of Ridge Lake, Fox Ridge State Park, Charleston, Illinois. 1951.*
No. 8. The Silting of Lake Chautauqua, Havana, Illinois. 1951.
No. 9. The Silting of Carbondale Reservoir, Carbondale, Illinois. 1951.*
No. 10. The Silting of Lake Bracken, Galesburg, Illinois. 1951.
No. 11. Irrigation in Illinois. 1951.
No. 12. The Silting of West Frankfort Reservoir, West Frankfort, Illinois. 1951.
No. 13. Studies of Thunderstorm Rainfall with Dense Raingage Networks and Radar. 1952.
No. 14. The Storm of July 8, 1951 in North Centra! Illinois. 1952.
No. 15. The Silting of Lake Calhoun, Galva, Illinois. 1952.
No. 16. The Silting of Lake Springfield, Springfield, Illinois, 1952.
No. 17. Preliminary Investigation of Groundwater Resources in the American Bottom. 1953.
No. 18. The Silting of Lake Carthage, Carthage, Illinois. 1953.
*Out of print.